Boron-Doped Ti 3 C 2 T x MXene for Effective and Durable High-Current-Density Ammonia Synthesis

Ammonia (NH ) synthesis via the nitrate reduction reaction (NO RR) offers a competitive strategy for nitrogen cycling and carbon neutrality; however, this is hindered by the poor NO RR performance under high current density. Herein, it is shown that boron-doped Ti C T MXene nanosheets can highly efficiently catalyze the conversion of NO RR-to-NH at ambient conditions, showing a maximal NH Faradic efficiency of 91% with a peak yield rate of 26.2 mgh mg , and robust durability over ten consecutive cycles, all of them are comparable to the best-reported results and exceed those of pristine Ti C T MXene. More importantly, when tested in a flow cell, the designed catalyst delivers a current density of ‒1000 mA cm at a low potential of ‒1.18 V versus the reversible hydrogen electrode and maintains a high NH selectivity over a wide current density range. Besides, a Zn-nitrate battery with the catalyst as the cathode is assembled, which achieves a power density of 5.24 mW cm and a yield rate of 1.15 mgh mg . Theoretical simulations further demonstrate that the boron dopants can optimize the adsorption and activation of NO RR intermediates, and reduce the potential-determining step barrier, thus leading to an enhanced NH selectivity.